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SPD_0090 Negatively Contributes to Virulence of Streptococcus pneumoniae.

ABSTRACT: In most bacteria, iron plays an important role in the survival of bacteria and the process of infection to the host. Streptococcus pneumoniae (S. pneumoniae) evolved three iron transporters (i.e., PiaABC, PiuABC, and PitABC) responsible for the transportation of three kinds of iron (i.e., ferrichrome, hemin, and ferric ion). Our previous study showed that both mRNA and protein levels of SPD_0090 were significantly upregulated in the ΔpiuA/ΔpiaA/ΔpitA triple mutant, but its detailed biological function is unknown. In this study, we constructed spd_0090 knockout and complement strain and found that the deletion of spd_0090 hinders bacterial growth. SPD_0090 is located on the cell membrane and affects the hemin utilization ability of S. pneumoniae. The cell infection model showed that the knockout strain had stronger invasion and adhesion ability. Notably, knockout of the spd_0090 gene resulted in an enhanced infection ability of S. pneumoniae in mice by increasing the expression of virulence factors. Furthermore, iTRAQ quantitative proteomics studies showed that the knockout of spd_0090 inhibited carbon metabolism and thus suppressed bacterial growth. Our study showed that SPD_0090 negatively regulates the virulence of S. pneumoniae.

SUBMITTER: Cao L

PROVIDER: S-EPMC9234739 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The bacterial factors responsible for the variation in invasive potential between different clones and serotypes of Streptococcus pneumoniae are largely unknown. Therefore, the isolation of rare serotype 1 carriage strains in Indigenous Australian communities provided a unique opportunity to compare the genomes of non-invasive and invasive isolates of the same serotype in order to identify such factors. The human virulence status of non-invasive, intermediately virulent and highly virulent serotype 1 isolates was reflected in mice and showed that whilst both human non-invasive and highly virulent isolates were able to colonize the murine nasopharynx equally, only the human highly virulent isolates were able to invade and survive in the murine lungs and blood. Genomic sequencing comparisons between these isolates identified 8 regions >1 kb in size that were specific to only the highly virulent isolates, and included a version of the pneumococcal pathogenicity island 1 variable region (PPI-1v), phage-associated adherence factors, transporters and metabolic enzymes. In particular, a phage-associated endolysin, a putative iron/lead permease and an operon within PPI-1v exhibited niche-specific changes in expression that suggest important roles for these genes in the lungs and blood. Moreover, in vivo competition between pneumococci carrying PPI-1v derivatives representing the two identified versions of the region showed that the version of PPI-1v in the highly virulent isolates was more competitive than the version from the less virulent isolates in the nasopharyngeal tissue, blood and lungs. This study is the first to perform genomic comparisons between serotype 1 isolates with distinct virulence profiles that correlate between mice and humans, and has highlighted the important role that hypervariable genomic loci, such as PPI-1v, play in pneumococcal disease. The findings of this study have important implications for understanding the processes that drive progression from colonization to invasive disease and will help direct the development of novel therapeutic strategies.

Project description:Streptococcus pneumoniae is the major cause of bacterial pneumonia, and it is also responsible for otitis media and meningitis in children. Apart from the capsule, the virulence factors of this pathogen are not completely understood. Recent technical advances in the field of bacterial pathogenesis (in vivo expression technology and signature-tagged mutagenesis [STM]) have allowed a large-scale identification of virulence genes. We have adapted to S. pneumoniae the STM technique, originally used for the discovery of Salmonella genes involved in pathogenicity. A library of pneumococcal chromosomal fragments (400 to 600 bp) was constructed in a suicide plasmid vector carrying unique DNA sequence tags and a chloramphenicol resistance marker. The recent clinical isolate G54 was transformed with this library. Chloramphenicol-resistant mutants were obtained by homologous recombination, resulting in genes inactivated by insertion of the suicide vector carrying a unique tag. In a mouse pneumonia model, 1.250 candidate clones were screened; 200 of these were not recovered from the lungs were therefore considered virulence-attenuated mutants. The regions flanking the chloramphenicol gene of the attenuated mutants were amplified by inverse PCR and sequenced. The sequence analysis showed that the 200 mutants had insertions in 126 different genes that could be grouped in six classes: (i) known pneumococcal virulence genes; (ii) genes involved in metabolic pathways; (iii) genes encoding proteases; (iv) genes coding for ATP binding cassette transporters; (v) genes encoding proteins involved in DNA recombination/repair; and (vi) DNA sequences that showed similarity to hypothetical genes with unknown function. To evaluate the virulence attenuation for each mutant, all 126 clones were individually analyzed in a mouse septicemia model. Not all mutants selected in the pneumonia model were confirmed in septicemia, thus indicating the existence of virulence factors specific for pneumonia.

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SPD_0090 Negatively Contributes to Virulence of Streptococcus pneumoniae.

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